Jellyfish can still sting days or even weeks after they die. This is because the stinging parts, called nematocysts or cnidocysts, remain active long after the jellyfish dies and can still be triggered by pressure. Even broken pieces of a jellyfish can sting — in 2010, bits of one dead lion's mane jellyfish stung 100-125 people. There are about 2,000 species of jellyfish, but only about 100 are dangerous to humans or other animals.
More facts about jellyfish: